Warehouses, manufacturing facilities, and large retail outlets typically include one or more loading docks for transferring goods to and from trucks, trailers, and other freight vehicles. Conventional loading docks usually consist of an exterior opening in a side of the building. The opening is typically covered by a roll-up door, and is usually positioned a few feet above the ground to be approximately level with trailer beds.
Some loading docks include a dock leveler that serves as movable ramp between the loading dock and the trailer bed. The aft edge of the ramp is typically attached to a hinge structure mounted to the floor of the loading dock, or to a rear wall of a dock leveler pit formed in the floor of the loading dock. The forward edge of the ramp typically carries a pivoting lip that hangs pendent until extended outwardly to set on the trailer bed. Various types of dock levelers and dock leveler features are disclosed in U.S. Pat. No. 5,475,888, U.S. Pat. No. 6,125,491 and U.S. Pat. No. 7,216,392, the disclosures of which are incorporated herein in their entireties by reference.
To load or unload goods from a trailer, the doors on the aft end of the trailer are opened and the trailer is backed up to the loading dock opening. The loading dock
To load or unload goods from a trailer, the doors on the aft end of the trailer are opened and the trailer is backed up to the loading dock opening. The loading dock door is raised and the dock leveler ramp is pivoted upwardly about the rear hinge to allow the lip to be extended outwardly and then downwardly onto the trailer bed. Workers, forklifts, etc., can then move in and out of the trailer to load and/or unload cargo. The ramp can move upwardly and downwardly about the rear hinge as necessary to accommodate movement of the trailer bed during the loading/unloading process.
There are various types of dock levelers. Powered dock levelers, for example, typically use hydraulic, pneumatic, and/or electric power, etc., to raise and lower the ramp into position for use. Mechanical dock levelers, however, typically require at least some physical effort on the part of the user to raise and/or lower the ramp. “Downward biased” mechanical dock levelers, for example, typically require the user to physically raise the ramp from the stored position for use. However, the ramp can descend through at least a portion of its downward motion under its own weight. “Upward biased” mechanical dock levelers can rise by themselves with the use of springs or some other type of stored energy when released from the lower, stored position. To extend the lip on some upward biased levelers, the user “walks down” the raised ramp using his or her weight to rotate the ramp downwardly and engage a lip lifting mechanism that pivots the lip outward as the ramp descends. Because the dock leveler is upwardly biased, a hold down mechanism is usually required to keep the ramp in the lowered position during use and when stored.
The hold down mechanisms typically used with conventional upwardly biased mechanical dock levelers often require frequent maintenance and adjustment to operate properly. Accordingly, one benefit of downwardly biased dock levelers is that they do not require a lock or hold down to keep them in the lowered position.